Certain types of network protocols append a set of labels or other metadata to a packet in order to specify the path that packet should take through a network. For example, multi-protocol label switching (MPLS) can specify by prefixing the packet with a list of network nodes through which the packet must pass. To implement such a protocol, each node within the network can maintain a forwarding table that stores the forwarding information usable to identify one or more paths from that node to a potential destination node. This forwarding information can be used when appending labels to a packet.
While these protocols work well during normal operations, difficulty may arise when network failures occur. For example, if a network node fails, the forwarding information that identifies that node may no longer be usable. Accordingly, each node that maintains forwarding table information identifying the now-failed node will need to update its forwarding table. Once each node that needs to do so has updated its forwarding information after a failure, and thus the network has converged on a new consistent state, the network is said to have reached post-convergence.
Nodes know to update their forwarding tables in response to receiving some sort of error indication. Unfortunately, given that different nodes and network links can be located at different distances from the failed node and/or have different operating characteristics, it is unlikely that each node will update its forwarding information at the same time. Accordingly, during the time after a failure (i.e., the time in which the network is converging), some nodes may still be using forwarding information that identifies the failed node or link. As a result of this, operating errors, such as loops within the network, may arise during the time the network is converging.
While the disclosure is susceptible to various modifications and alternative forms, specific embodiments are provided as examples in the drawings and detailed description. It should be understood that the drawings and detailed description are not intended to limit the disclosure to the particular form disclosed. Instead, the intention is to cover all modifications, equivalents and alternatives falling within the spirit and scope of the appended claims.